diff --git a/beacon_node/beacon_chain/src/beacon_chain_builder.rs b/beacon_node/beacon_chain/src/beacon_chain_builder.rs
index 8a5190048..a569fe833 100644
--- a/beacon_node/beacon_chain/src/beacon_chain_builder.rs
+++ b/beacon_node/beacon_chain/src/beacon_chain_builder.rs
@@ -130,6 +130,10 @@ fn genesis_block<T: EthSpec>(genesis_state: &BeaconState<T>, spec: &ChainSpec) -
     genesis_block
 }
 
+/// Builds a genesis state as defined by the Eth2 interop procedure (see below).
+///
+/// Reference:
+/// https://github.com/ethereum/eth2.0-pm/tree/6e41fcf383ebeb5125938850d8e9b4e9888389b4/interop/mocked_start
 fn interop_genesis_state<T: EthSpec>(
     validator_count: usize,
     genesis_time: u64,
diff --git a/eth2/state_processing/src/per_block_processing/tests.rs b/eth2/state_processing/src/per_block_processing/tests.rs
index cf64dc85e..f419d5fae 100644
--- a/eth2/state_processing/src/per_block_processing/tests.rs
+++ b/eth2/state_processing/src/per_block_processing/tests.rs
@@ -1,4 +1,5 @@
 #![cfg(all(test, not(feature = "fake_crypto")))]
+
 use super::block_processing_builder::BlockProcessingBuilder;
 use super::errors::*;
 use crate::{per_block_processing, BlockSignatureStrategy};
diff --git a/eth2/state_processing/tests/tests.rs b/eth2/state_processing/tests/tests.rs
index 43b66f3ed..a7390c850 100644
--- a/eth2/state_processing/tests/tests.rs
+++ b/eth2/state_processing/tests/tests.rs
@@ -1,3 +1,5 @@
+#![cfg(not(feature = "fake_crypto"))]
+
 use state_processing::{
     per_block_processing, test_utils::BlockBuilder, BlockProcessingError, BlockSignatureStrategy,
 };
diff --git a/eth2/utils/bls/src/public_key_bytes.rs b/eth2/utils/bls/src/public_key_bytes.rs
index f75735140..afdbcb270 100644
--- a/eth2/utils/bls/src/public_key_bytes.rs
+++ b/eth2/utils/bls/src/public_key_bytes.rs
@@ -31,6 +31,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg(not(feature = "fake_crypto"))]
     pub fn test_invalid_public_key() {
         let mut public_key_bytes = [0; BLS_PUBLIC_KEY_BYTE_SIZE];
         public_key_bytes[0] = 255; //a_flag1 == b_flag1 == c_flag1 == 1 and x1 = 0 shouldn't be allowed
diff --git a/eth2/utils/bls/src/signature_bytes.rs b/eth2/utils/bls/src/signature_bytes.rs
index a30cecb4d..b89c0f0d1 100644
--- a/eth2/utils/bls/src/signature_bytes.rs
+++ b/eth2/utils/bls/src/signature_bytes.rs
@@ -32,6 +32,7 @@ mod tests {
     }
 
     #[test]
+    #[cfg(not(feature = "fake_crypto"))]
     pub fn test_invalid_signature() {
         let mut signature_bytes = [0; BLS_SIG_BYTE_SIZE];
         signature_bytes[0] = 255; //a_flag1 == b_flag1 == c_flag1 == 1 and x1 = 0 shouldn't be allowed